Transcriptome and DNA methylome analysis reveal new insights into methyl jasmonate-alleviated chilling injury of peach fruit after cold storage

Methyl jasmonate (MeJA) has been used to alleviate the chilling injury (CI) caused by postharvest cold storage of horticultural crops involving peach fruit. However, the molecular mechanism remains largely unknown. Here, we treated melting peach fruit (Prunus persica L. Batsch., cv. Hujingmilu) with different concentrations of MeJA, followed by storage at 0 °C up to 28 d. Peach fruit treated with 1 mM MeJA delayed the development of CI during 3 d shelf-life followed by 28 d cold after storage (C28dS3). The alleviated CI was associated with significant higher content of JA-Ile in peach fruit after MeJA treatment than controls. RNA-Seq revealed significant alternations in expression of genes related to ethylene synthesis, fruit softening, flesh browning and aroma-related volatile synthesis. Transcription factors associated with fruit ripening such as PpNAC1 and JA signaling such as PpMYC2.2 showed higher transcript levels in MeJA treated peach fruit than controls. Peach fruit with CI symptom had higher genome methylation level than MeJA treated fruit after cold storage at C28dS3. Reverse patterns between transcript abundance and DNA methylation in promoter were observed for transcription factor PpNAC1 and downstream PpACS1 for ethylene synthesis, PpExp1 for softening, and PpAAT1 for volatile ester and lactone production. Overall, in addition to providing new insights into the regulatory mechanism for MeJA in alleviating fruit chilling injury through integration of transcriptome and DNA methylome, our study also establishes a foundation for fruit quality maintaining after cold storage of peach fruit.